IC 2118, Witch Head Nebula

IC 2118
IC 2118: Witch Head Nebula in Eridanus; 4.5" Vixen ED115 Reducer f/5.2, Canon EOS 20Da; 150 min, 1600 ISO; Observatory Schlierental, Obwalden; © 2008 Eduard von Bergen

History

The Witch Head Nebula was discovered on December 20, 1786 by William Herschel with his 18.7 inch reflector telescope with a focal length of 20 feet and recorded as V 38. He noted: «strongly suspected very large nebula, not less than 2° 11' in pole distance (declination) and 26 seconds in right ascension.» [464] In Dreyer's «New General Catalogue» [313] published in 1888, this entry was given the designation NGC 1909. Unfortunately, in Herschel's second part of his catalog, published in 1789 [464], an error had crept in: he always determined the position of the nebulae he discovered relatively to known stars and this time used the star Rigel (β Orionis). However, the nebula was indicated for around 11 minutes in right ascension east instead of west (f for following, instead of p for preceeding). At the position it noted there was nothing to be found that The nebula was then rediscovered by Max Wolf on January 16, 1891, and in Dreyer's «Index Catalogue» [314] it was given the designation IC 2118, which commonly used today. [196]

Physical Properties

IC 2118 is a dust cloud near the bright star Rigel (β Orionis), which reflects and scatters the bluish-white light from the star. Both are about 800 light years away. Presumably it is the remnant of a supernova or parts of a gas bubble, which is blown away by the hot stars in Orion's belt and in the Orion Nebula, which also includes the Barnard Loop east of the constellation Orion. [196, 253]

Observations with radio telescopes show a considerable occurrence of carbon monoxide emissions, an indication of the presence of molecular clouds and star formation in the nebula. Candidates for a precursor to the main sequence stars and some classic T-Tauri stars were found in the nebula. [254]

«Revised New General Catalogue and Index Catalogue», «Historically Corrected New General Catalogue», Dr. Wolfgang Steinicke, 2021 [277]
NameRADecTypeBmagVmagDimDreyer DescriptionIdentification
NGC 1909 05 25 54.0-08 01 00NFeL, strongly susp (2° in PD)
IC 2118 05 04 54.0-07 15 00RN180.00 × 60.0F, eL, iF, III 500 inv sLBN 959, CED 41, Witch Head nebula

Finder Chart

The Witches Head Nebula is located at the source of the Eridanus River, just under 2.5° west of the star Rigel (β Orionis). It is a large, faint reflection nebula.

Chart IC 2118
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

References

149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
253Witch Head Nebula; nasa.gov/multimedia/imagegallery/image_feature_1209.html (2021-01-30)
254«The IC2118 association: new T Tauri stars in high-latitude molecular clouds» M. Kun, T. Prusti, S. Nikoli'c, L. E. B. Johansson, N. A. Walton; arXiv:astro-ph/0402353; DOI:10.1051/0004-6361:20034510
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
314«Index Catalogue of Nebulæ found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue» Dreyer, J. L. E.; Memoirs of the Royal Astronomical Society, Vol. 51, p.185; 1895; Bibcode:1895MmRAS..51..185D
464«Catalogue of a second thousand of new nebulae and clusters of stars; with a few introductory remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1789; DOI:10.1098/rstl.1789.0021